Generally, a vehicular tailgate (or engine hood, trunk lid or the like) is mounted with a gas lifter to maintain the opened state of the tailgate. The tailgate is typically larger and heavier than a vehicle door, and should easily be opened and closed with a small amount of power. Further, the tailgate should remain opened when the tailgate is completely opened.
The conventional gas lifter used for the tailgate to generate high pressure gas is superior in correcting the gas pressure of the cylinder. However, the gas lifter has been difficult to use in practice due to its heavy weight, expensive material cost, significant occupation of an installment area and difficulty of manufacture. For other methods, the hinge structure is modified or pressure in the cylinder is manually changed to improve the opening and closing function of the tailgate. However, an excessive force is required for opening the tailgate or the tailgate may close suddenly, causing potential injury to the user in case his or her body part gets stuck between the vehicle body and tailgate.